In the manufacture of electronic circuits, a number of silicon chips may be combined into a single package which must then be electrically connected to the circuits on the underlying substrate, such as a printed circuit board. Leadless chip carriers are frequently used for this purpose because of their relatively low cost, sturdiness and ease of handling. Generally, they are connected to the underlying printed circuit board by means of soldered electrical connections between the chip and metallized pads that are positioned on the printed circuit board under or adjacent the carrier body. A disadvantage of this type of device is the susceptiblity to stress-cracking of the solder connection. Such cracking may be caused by the small differential movement between the circuit board and the carrier due to unequal expansion of these components during operational heating and cooling cycles. Typically, the substrate or circuit board may consist of a fiber-reinforced resin composite material, with a coefficient of expansion which is different from that of the ceramic material used for the chip carrier.
Another problem that may occur when a leadless chip carrier is used derives from the portion of the solder material which is deliberately deposited underneath the carrier body in order to enhance the electrical connection. Solder material in that area is stressed to a greater extent than the solder fillet adjacent the carrier and, thus, cracks are more likely to originate in that area upon unequal expansion or contraction of the board and carrier.